1. Field of the Invention
The present invention relates to a method and an apparatus for cleaning closed spaces. More particularly, it relates to a method and an apparatus for trapping and removing by means of electric charging fine particles present in closed spaces.
The cleaning method and apparatus of the present invention find extensive use in the home, business offices and various industries including those of semiconductors, fine chemicals, foods, agriculture and forestry, pharmaceuticals and precision machines in cleaning closed spaces in clean rooms and germ-free rooms, as exemplified by safety cabinets, clean boxes, safes, wafer storage spaces, closed spaces for transporting valuables, clean closed spaces (either filled with various gases or in vacuo), the closed spaces of various CVD apparatus and film forming apparatus, as well as spaces wherein robots operate.
2. Prior Art
The prior art is described below with reference to FIG. 2 taking as an example the case of purifying gases in wafer storages in the semiconductor industry.
In the system shown in FIG. 2, the wafer storage space 1 which provides a closed space contains a gas 2 which is to be purified by means of a fan 3 and a high-performance filter 4. The gas 2 in the wafer storage 1 is aspirated by the fan 3 and passed through the high-performance filter 4 so that any fine particles in the gas 2 are trapped and removed to purify the gas. Since the space (or site) 1 to be cleaned is distant from the site 4 of dust collection for purification, the gas to be purified must be fluidized by the fan.
The prior art method described above is limited in its ability to purify gases and, for efficient purification, the number of times the gas 2 is circulated through the high-performance filter 4 has to be increased resulting in an increase in power consumption.
Further, with the space (site) 1 to be cleaned being remote from the site 4 of dust collection for purification, the gas has to be fluidized and this can cause problems such as the evolution of fine particles.
Also, if the closed space is in vacuo, the evolved fine particles cannot be trapped and removed rapidly from the vacuum space.